The disclosure relates in general to medium-dependent interface crossover (MDIX) circuits. In particular, the disclosure relates to MDIX circuits with a switching current mode.
Medium-dependent interface (MDI)/MDIX is a type of Ethernet port connection using twisted pair cabling. The MDI is the component of the media attachment unit (MAU) that provides the physical and electrical connection to the cabling medium. An MDIX (for MDI crossover) is a version of MDI that enables connection between like devices. MDI ports connect to MDIX ports via straight-through twisted pair cabling, both MDI-to-MDI and MDIX-to-MDIX connections use crossover twisted pair cabling.
Many local area network (LAN) products use a medium consisting of twisted pair copper wire pairs for the transmission and reception of data. It is generally a requirement that one or more pairs be used for transmission of data in one direction and one or more other pairs to receive data in the opposite direction. The connection between two node devices is a link. Many LAN devices, which employ a full-duplex medium, have different pairs for transmission than for reception and require, therefore, that each end of the link use a defined assignment for its twisted pair connector to a particular pair of wires. If the transmitting pair of wires of one device is connected to the transmitting connectors of another, obviously the communication link will fail.
Most LAN standards address this problem by assigning different connector pins to the wires in the twisted pair at the RJ-45, often referred to as the medium-dependent interface (MDI). In switched networks, Network Interface Devices (NIC) may be directly connected to another NIC, or a repeater may be connected to another repeater, or a repeater may alternately be connected to a switch. Depending upon the assignment of pins in the network interface, it is sometimes necessary to use a crossover cable to address the problem of both products using the same pin designations on their interfaces. Determining whether the interface requires this cable can cause confusion and frustration if the customer lacks the necessary cable. To get around this problem, some products use a manual “MDIX” switch, which still, however, requires user intervention.